TW202016515A - Ambient light sensor - Google Patents

Abstract

An ambient light sensor is provided, which includes a photoelectric element, an adjustable capacitor, an operational amplifier, a comparator, a pulse generator circuit and a accumulator circuit. The photoelectric element converts light energy into a photocurrent. The adjustable capacitor is connected between a first input terminal and an output terminal of the operational amplifier. A capacitance of the adjustable capacitor is adjusted according to the photocurrent value. The operational amplifier outputs an error amplification signal based on a voltage difference between an input voltage at its first input terminal and a reference voltage at its second input terminal. The comparator outputs a comparison signal when the input voltage is greater than the reference voltage. The pulse generator circuit outputs a pulse signal based on the comparison signal, the accumulator circuit accumulates the number of times that the input voltage is raised to a voltage greater than the reference voltage.

Description

Ambient light sensor

The invention relates to an ambient light sensor, and in particular to an ambient light sensor that can accurately sense the ambient light intensity in a short time.

Consumer electronics products, such as mobile phones, use more and more sensors to save energy and improve the interaction between humans and machines. For example, more than ten sensors are used in the latest mobile phones. Therefore, engineers are actively seeking ways to integrate sensors in order to reduce energy, space and cost.

The ambient light sensor (ambient light sensor) is used to sense changes in the ambient light source and change the brightness of the mobile phone panel. When the surrounding brightness is dark, the brightness of the panel is darkened to avoid eye irritation. When the outdoor light source is strong, the backlight of the mobile phone panel will be brightened to increase visibility. The ambient light sensor changes the brightness of the panel according to the ambient light source, and can also achieve energy saving effects and increase the use time of the mobile phone. Proximity sensor is a non-contact object detection sensor. It is used in mobile devices, such as the anti-touch function of the mobile phone. Once the user's head is close to the earpiece, the mobile phone's touch function will be Automatically shuts down to prevent accidental touch of functions caused by contact between face and panel when talking on the phone. Since both the ambient light sensor and the proximity sensor are also optical systems that sense light intensity and operate, they are integrated into a package structure to share space, consumables, and merge power supply circuit layouts.

In order to solve the lack of conventional technology, the object of the present invention is to provide an ambient light sensor suitable for electronic devices. The electronic device includes a capacitance control circuit. The ambient light sensor includes a first photoelectric element, a variable capacitor, an operational amplifier, a comparator, a pulse wave generating circuit, and a pulse wave accumulator circuit. The first photovoltaic element has a first positive terminal and a first negative terminal. The first positive terminal of the first photovoltaic element is grounded. The first photovoltaic element is configured to convert light energy irradiated through the first photovoltaic element into a photocurrent. The variable capacitor is connected to the capacitance control circuit. The capacitance control circuit is configured to adjust the capacitance value of the variable capacitor according to the photocurrent value. The variable capacitor receives photocurrent. The operational amplifier has a first amplification input terminal and a second amplification input terminal, which are respectively connected to the first negative terminal of the first photoelectric element and the reference voltage source. A variable capacitor is connected between the output terminal of the operational amplifier and the first amplification input terminal. The operational amplifier is configured to output an error amplification signal based on the difference between the voltage of the first amplification input terminal and the voltage of the reference voltage source and the gain value of the operational amplifier. The comparator has a first comparison input terminal and a second comparison input terminal, respectively connected to the output terminal of the operational amplifier and the reference voltage source. The comparator is configured to compare the error amplification signal and the reference voltage source to output the comparison signal. The pulse wave generating circuit is connected to the output of the comparator. The pulse wave generating circuit is configured to determine that the voltage of the first comparison input terminal of the comparator is greater than the voltage of the reference voltage source according to the comparison signal, and the output pulse signal has a rising or falling edge of the waveform aligned with the voltage waveform of the first comparison input terminal The voltage of rises from a voltage less than the reference voltage source to a momentary point equal to the voltage of the reference voltage source. The pulse wave accumulator circuit is connected to the pulse wave generating circuit and the output end of the comparator. The pulse wave accumulator circuit realizes counting when the voltage of the comparison signal at the first comparison input terminal rises from a voltage less than the reference voltage source to a voltage greater than the reference voltage source.

As described above, compared to the conventional ambient light sensor with only a small number of photoelectric elements, it takes a relatively long sensing time when the light intensity of the ambient light source is small. In order to save the sensing time, the traditional ambient light sensor is further improved A large number of photoelectric elements are required in the detector, and these large amounts of photoelectric elements occupy the empty space of the integrated circuit in the electronic device Time, the size of the electronic device cannot be reduced. Therefore, the ambient light sensor provided by the present invention can increase the configuration of the variable capacitance and the pulse wave generating circuit and other circuit elements, so that only a small number (only two) of photoelectric elements can be provided to save the cost of circuit element arrangement and shrink Under the condition of occupying space, the light intensity of the ambient light source can be accurately sensed in a short time, so that the electronic device can adjust the display screen to have a brightness more in line with the desired result according to the sensing result of the ambient light sensor.

1‧‧‧Electronic device

10‧‧‧Ambient light sensor

20‧‧‧Capacitance control circuit

30‧‧‧Control circuit

100‧‧‧Operational amplifier

EAO1, EAO11, EAO2, EAO3 ‧‧‧ error amplification signal

200‧‧‧Comparator

CMP1, CMP2, CMP3 ‧‧‧ comparison signal

300‧‧‧Logic circuit

SET‧‧‧Setting

RESET‧‧‧Reset

‧‧‧輸出端 Q,

‧‧‧Output

LOG1, LOG2, LOG3 ‧‧‧ logic signals

400‧‧‧Counting circuit

410‧‧‧Pulse Accumulator Circuit

D‧‧‧Input

CK‧‧‧Clock end

CON1, CON2, CON3‧‧‧ times

500‧‧‧Pulse wave generating circuit

PG2, PG3 ‧‧‧ Pulse signal

600‧‧‧storage circuit

610‧‧‧pulse wave storage circuit

REG1, REG2, REG3 ‧‧‧ store signal

CLKL1, CLKR1 ‧‧‧ clock signal

IT_EN‧‧‧Enable signal

C1‧‧‧Variable capacitance

S1, S2‧‧‧Switch element

M1‧‧‧ Current mirror circuit

T1, T2‧‧‧transistor

C2‧‧‧Fixed capacitor

PD1, PD2

Iph‧‧‧Photocurrent

Idark‧‧‧Dark current

SH‧‧‧Shading element

VREF‧‧‧Reference voltage source

IREF‧‧‧Variable current source

IREF2‧‧‧constant current source

Gain‧‧‧Gain

FIG. 1 is a block diagram of internal components of an electronic device using an ambient light sensor according to a first embodiment of the invention.

FIG. 2 is a circuit layout diagram of an ambient light sensor applied to an electronic device according to a first embodiment of the invention.

3 is a waveform diagram of the error amplification signal output by the operational amplifier of the ambient light sensor and the received reference voltage signal according to the first embodiment of the present invention.

4 is a circuit layout diagram of an ambient light sensor applied to an electronic device according to a second embodiment of the invention.

FIG. 5 is a circuit layout diagram of an ambient light sensor applied to an electronic device according to a third embodiment of the invention.

6 is an error amplification signal output by an operational amplifier of an ambient light sensor according to a third embodiment of the present invention, a comparison signal output by a comparator, a logic signal output by a logic circuit, the number of times the pulse accumulator circuit counts, and input to The waveform diagram of the enable signal of the pulse wave storage circuit.

7 is a graph of the photocurrent of the photoelectric element of the ambient light sensor of the third embodiment of the present invention versus the number of counts of the pulse wave accumulator circuit.

FIG. 8 is a graph of the photocurrent of the photoelectric element of the conventional ambient light sensor versus the count times of the counting circuit.

The following are specific specific examples to illustrate the embodiments of the present invention disclosed by the present invention. Those skilled in the art can understand the advantages and effects of the present invention from the contents disclosed in this specification. The present invention can be implemented or applied through other different specific embodiments. Various details in this specification can also be based on different viewpoints and applications, and various modifications and changes can be made without departing from the concept of the present invention. In addition, the drawings of the present invention are merely schematic illustrations, and are not drawn according to actual sizes, and are declared in advance. The following embodiments will further describe the related technical content of the present invention in detail, but the disclosed content is not intended to limit the protection scope of the present invention.

It should be understood that although the terms first, second, third, etc. may be used herein to describe various elements or signals, these elements or signals should not be limited by these terms. These terms are mainly used to distinguish one component from another component, or one signal from another signal. In addition, the term "or" as used herein may include any combination of any one or more of the associated listed items, depending on the actual situation.

For clarity of explanation, in some cases, the present technology may be presented as an independent functional block including functional blocks, which include devices, device elements, steps or routes in methods implemented in software, or a combination of hardware and software.

The device implementing the methods according to these disclosures may include hardware, firmware, and/or software, and may take any of various shapes. Typical examples of this form include notebook computers, smart phones, small personal computers, personal digital assistants, and so on. The functions described in this article can also be implemented in peripheral devices or built-in cards. By way of further example, this function can also be implemented on different chips or on different circuit boards executed on a single device.

The instructions, the medium for transmitting such instructions, the computing resources for executing them, or other structures for supporting such computing resources are means for providing the functions described in these disclosures.

[First embodiment]

Please refer to FIG. 1, which is the electrical diagram of the ambient light sensor according to the first embodiment of the present invention. Block diagram of the internal components of the child device. As shown in FIG. 1, the ambient light sensor 10 of the embodiment of the present invention can be applied to an electronic device 1 such as a mobile device. The ambient light sensor 10 can be arranged corresponding to the position of the display screen of the electronic device 1 to sense the light intensity of the ambient light source illuminating the display screen of the electronic device 1, such as the intensity of indoor and outdoor ambient light sources. It is worth noting that the electronic device 1 can instruct the capacitance control circuit 20 through the control circuit 30 to adjust the time and accuracy of the ambient light sensor 10 sensing. The control circuit 30 of the electronic device 1 can adjust the brightness of the display screen of the electronic device 1 according to the sensing result of the ambient light sensor 10.

Please also refer to FIG. 2, which is a circuit layout diagram of an ambient light sensor applied to an electronic device according to a first embodiment of the present invention. As shown in FIG. 2, the ambient light sensor 10 of the embodiment of the present invention is applied to the capacitance control circuit 20 and the control circuit 30 of the electronic device 1. The ambient light sensor 10 includes an operational amplifier 100, a comparator 200, a logic circuit 300, a counting circuit 400, a storage circuit 600, photoelectric elements PD1, PD2, a variable capacitor C1, a current mirror circuit M1, and switching elements S1, S2.

。 The photovoltaic element PD1 and the photovoltaic element PD2 are connected in parallel to each other. The inverting input terminal of the operational amplifier 100 is connected to the negative terminals of the photoelectric elements PD1 and PD2. The positive terminals of the photoelectric elements PD1 and PD2 are grounded. The non-inverting input terminal of the operational amplifier 100 is connected to the reference voltage source VREF. The switching element S2 is connected in parallel with the variable capacitor C1. The variable capacitor C1 and the switching element S2 are connected between the output terminal and the inverting input terminal of the operational amplifier 100. The first end of the switching element S1 is connected to a variable current source IREF, which provides a variable current, but the present invention is not limited to this, in practice, it can also be replaced by a constant current source IREF2 as shown in FIG. 4; The second end of the element S1 is connected to the switching element S2, and the control end of the switching element S1 is connected to the output end of the logic circuit 300

.

The variable capacitor C1 can be wirelessly or wiredly connected to the capacitance control circuit 20 of the electronic device 1 to adjust the capacitance value of the variable capacitor C1 through the capacitance control circuit 20 of the electronic device 1. For example, in this embodiment, the variable capacitor C1 is connected in series with the capacitance control circuit 20. In practice, the variable capacitor C1 can also be directly touched by a human hand, instead of the capacitance control circuit 20 to adjust the capacitance value of the variable capacitor C1.

The current mirror circuit M1 can be selectively provided. The input terminal of the current mirror circuit M1 can be connected to a voltage source or a current source. The two output terminals of the current mirror circuit M1 are respectively connected to the negative terminal of the photoelectric element PD1 and the negative terminal of the photoelectric element PD2. For example, the current mirror circuit M1 includes a PMOS transistor T1 and a PMOS transistor T2. The source terminals of the transistor T1 and the transistor T2 are connected to a current source or a voltage source. The gate terminal of the transistor T1 is connected to the gate terminal of the transistor T2 and the drain terminal of the transistor T1. The drain terminal of the transistor T1 is connected to the negative terminal of the photovoltaic element PD2, and the drain terminal of the transistor T2 is connected to the negative terminal of the photovoltaic element PD1.

The non-inverting input terminal of the comparator 200 is connected to the output terminal of the operational amplifier 100, and the inverting input terminal of the comparator 200 is connected to the reference voltage source VREF. The output terminal of the comparator 200 is connected to the setting terminal SET of the logic circuit 300. The reset terminal RESET of the logic circuit 300 can be connected to an additional clock circuit to obtain the clock signal CLKL1. In this embodiment, the logic circuit 300 and the counting circuit 400 are S-R and D-type flip-flops, respectively. In practice, other logic circuit components can be replaced as required, and the invention is not limited to this.

The output terminal Q of the logic circuit 300 is connected to the input terminal D of the counting circuit 400. The clock terminal CK of the counting circuit 400 can be connected to an additional clock circuit to obtain the clock signal CLKL1. The output terminal of the counting circuit 400 is connected to the storage circuit 600. For example, the storage circuit 600 may be a register or other circuit element with a storage function. The output end of the storage circuit 600 can be connected to a serial interface of the electronic device 1, such as an I2C interface, and is connected to the control circuit 30 through the serial interface.

In addition, the control circuit 30 can contact the negative ends of the photoelectric elements PD1 and PD2 or the lines connected to the negative ends of the photoelectric elements PD1 and PD2 to detect and obtain the photocurrent Iph generated by the photoelectric element PD1 and the dark current generated by the photoelectric element PD2 Idark. Alternatively, the photoelectric current Iph generated by the photoelectric element PD1 and the dark current Idark generated by the photoelectric element PD2 are detected and obtained by the capacitance control circuit 20.

It is worth noting that, in order to sense the light source with a small light intensity of the surrounding environment in a short time, the traditional ambient light sensor needs to set a large number of internal, such as 64 photoelectric Sensor. In addition, since the photoelectric sensor will generate dark current (also called leakage current) without being irradiated by the ambient light source, the traditional electronic device needs to be provided with the same number of photoelectric sensors as the ambient light source. Another group is for example 64 photoelectric sensors. Therefore, in order to sense the correct light intensity, a large number of photoelectric sensors, such as a total of 128 photoelectric sensors, need to be provided in the traditional electronic device to generate a photocurrent through one set of photoelectric sensors when illuminated by the ambient light source Another set of photoelectric sensors produces dark current without being irradiated by the ambient light source, and calculates the subtraction value of the photocurrent and the dark current to obtain the actual current value corresponding to the ambient light intensity. Therefore, if the conventional electronic device needs to accurately adjust the brightness of the display screen according to the actual current value, a large number of photoelectric sensors need to be installed, occupying the integrated circuit space in the electronic device, resulting in the size of the electronic device being unable to be reduced.

In contrast, in the embodiment of the present invention, only a single photoelectric element PD1 is used to generate a photocurrent Iph through the photoelectric element PD1 when the ambient light source is irradiated, and a single photoelectric sensor PD2 is correspondingly provided to generate a dark current. As shown in FIG. 2, when an ambient light source, such as sunlight or light, passes through the photoelectric element PD1, the photoelectric element PD1 converts the light energy supplied by the ambient light source into a photocurrent Iph. The photocurrent Iph value is proportional to the light intensity. The photocurrent Iph then flows to the variable capacitor C1 to charge the variable capacitor C1.

It should be understood that when the capacitance value of the variable capacitor C1 is fixed, the smaller the light intensity of the ambient light source results in a smaller photocurrent Iph each time, the longer the operation amplifier will charge the variable capacitor C1, and Even if the voltage at the non-inverting input of the comparator rises above the voltage of the reference voltage source VREF received by the inverting input of the comparator, the longer it takes. Conversely, the greater the light intensity of the ambient light source, the shorter the charging time of the variable capacitor C1.

In order to make the ambient light sensor 10 have good sensing efficiency when the light intensity of the ambient light source is small, and even to have the same sensing time when generating different magnitudes of photocurrent Iph, the electronic device 1 can adjust the environment The capacitance value of the variable capacitance C1 of the photo sensor 10. Specifically, the electronic device 1 can pass electricity connected in series with the variable capacitor C1 The current detector in the capacity control circuit 20, or in practice, the current detector in the control circuit 30 or other additional current detectors, to detect the photocurrent Iph to be passed through the variable capacitor C1.

The capacitance control circuit 20 of the electronic device 1 can determine the adjustment range of the capacitance value of the variable capacitor C1 according to the sensed photocurrent Iph value. When the photocurrent Iph value is less than the preset photocurrent value pre-stored by the capacitance control circuit 20, the capacitance control circuit 20 can adjust the capacitance value of the variable capacitor C1 and the capacitance control circuit 20 or other control circuit elements can be adjusted The current value provided by the current source IREF reduces the time for charging the voltage of the variable capacitor C1 from the zero value to the target voltage value through the smaller photocurrent Iph.

Conversely, when the photocurrent Iph value is greater than the photocurrent preset value pre-stored by the capacitance control circuit 20, the capacitance control circuit 20 may not adjust or increase the capacitance value of the variable capacitor C1 and the current of the variable current source IREF to pass through The time for the larger photocurrent Iph to charge the voltage of the variable capacitor C1 from the zero value to the target voltage value is substantially the same as the charging time for the above-mentioned transmission and the smaller photocurrent Iph and this time is less than the time threshold.

The operational amplifier 100 calculates the difference between the input voltage of the inverting input terminal of the operational amplifier 100 and the voltage of the reference voltage source VREF received by the non-inverting input terminal of the operational amplifier 100. The operational amplifier 100 multiplies this difference by the gain value of the operational amplifier 100, and outputs the corresponding error amplification signal EAO1 according to this product value.

When the non-inverting input terminal of the comparator 200 receives the error amplification signal EAO1, the comparator 200 compares the difference between the voltage of the waveform of the error amplification signal EAO1 and the voltage of the reference voltage source VREF received by the inverting input terminal of the comparator 200, To output the comparison signal CMP1. For example, when the voltage value of the waveform of the error amplification signal EAO1 is greater than the voltage value of the reference voltage source VREF, the comparator 200 outputs the comparison signal CMP1 representing the high logic level 1. Conversely, when the voltage value of the waveform of the error amplification signal EAO1 is less than the voltage value of the reference voltage source VREF, the comparator 200 outputs the comparison signal CMP1 representing a low level logic zero.

When the setting terminal SET of the logic circuit 300 receives the comparison signal CMP1 having a waveform that reaches the reference level, for example, the logic level is 1, and the logic circuit 300 receives the comparison signal CMP1 representing the high level logic 1 from the comparator 200, The high-level logic signal LOG1 is output to the counting circuit 400.

When the counting circuit 400 receives the high-level logic signal LOG1, the counting circuit 400 counts the voltage of the non-inverting input terminal of the comparator 200 from the voltage less than the reference voltage source VREF to the voltage greater than the reference voltage source VREF based on the comparison signal CMP1 CON1. The counting time length of the counting circuit 400 depends on the time length of the cycle of the clock signal CLKL1 waveform that triggers the counting circuit 400. The counting circuit 400 may output the counting times CON1 to the storage circuit 600 for storage. After the counting is completed, the logic circuit 300 can be triggered to reset by the positive edge of the pulse signal CLK1.

The storage circuit 600 can output the corresponding storage signal REG1 to the control circuit 30 of the electronic device 1 according to the count number CON1. The control circuit 30 of the electronic device 1 can adjust the amplitude of the variable capacitor C1 according to the storage signal REG1 from the storage circuit 600 and the capacitance control circuit 20 to determine the light intensity of the current ambient light source, and adjust the display screen of the electronic device 1 accordingly brightness.

In order for the electronic device 1 to adjust the screen brightness of the display screen more accurately. The ambient light sensor 10 is additionally provided with a photoelectric element PD2, which is connected in parallel with the photoelectric element PD1. The negative terminals of the photoelectric elements PD1 and PD2 are connected to the inverting input terminal of the operational amplifier 100, and the positive terminals of the photoelectric elements PD1 and PD2 are grounded. The light-shielding element SH may be configured to shield the photovoltaic element PD2 to prevent the ambient light source from illuminating through the photovoltaic element PD2.

The detection element in the control circuit 30 of the electronic device 1 can detect the photocurrent Iph generated by the photoelectric element PD1 of the ambient light sensor 10 being irradiated by the ambient light source, and the dark current generated by the photoelectric element PD2 without being illuminated by any light source Idark. In this embodiment, the photovoltaic element PD1 and the photovoltaic element PD2 have the same characteristics. The photocurrent Iph generated by the photoelectric element PD1 is the sum of the dark current Idark and the actual current converted by ambient light energy. Therefore, the control circuit 30 of the electronic device 1 subtracts the photocurrent Iph and the dark current Idark to obtain the actual current, which can be based on the actual conversion of the corresponding ambient light source Current to adjust the screen brightness of the electronic device 1 more accurately.

則輸出邏輯0至開關元件S1，此時開關元件S1為導通狀態。相反地，當邏輯電路300的輸出端Q產生邏輯0而邏輯電路300的輸出端

輸出邏輯1時，此時開關元件S1為截止狀態，計數電路400不進行計數作業，而是透過光電元件PD1產生的光電流Iph放電可變電容C1之前的初始調整值，或是說運算放大器對可變電容C1進行充電作業。邏輯電路300的輸出端

輸出邏輯0至開關元件S1可控制開關元件S1運作，可變電流源IREF可供應電流導通開關元件S1、S2，使光電元件PD1產生的光電流Iph或其他電流皆不流過可變電容C1而是通過開關元件S2。 In addition, when the output terminal Q of the logic circuit 300 generates a logic 1 to indicate that a counting operation is in progress, the output terminal of the logic circuit 300

Then, a logic 0 is output to the switching element S1, and the switching element S1 is in an on state at this time. Conversely, when the output Q of the logic circuit 300 produces a logic 0 and the output of the logic circuit 300

When logic 1 is output, the switching element S1 is turned off, and the counting circuit 400 does not perform the counting operation, but discharges the initial adjustment value before the variable capacitor C1 through the photocurrent Iph generated by the photoelectric element PD1, or the operational amplifier pair The variable capacitor C1 performs charging operation. The output of the logic circuit 300

Output logic 0 to the switching element S1 can control the operation of the switching element S1. The variable current source IREF can supply current to turn on the switching elements S1 and S2, so that the photocurrent Iph or other currents generated by the photoelectric element PD1 do not flow through the variable capacitor C1. It is through the switching element S2.

Please refer to FIG. 3 together, which is a waveform diagram of the error amplification signal output by the operational amplifier of the ambient light sensor according to the first embodiment of the present invention and the received reference voltage signal.

The upper waveform shown in FIG. 3 represents the error amplification signal EAO1 output by the operational amplifier 100 when the gain Gain is doubled. The lower waveform shown in FIG. 3 represents the error amplification signal EAO11 output by the operational amplifier 100 when the gain Gain is doubled. As shown in FIG. 3, the error amplification signal EAO11 is twice that of the error amplification signal EAO1, which means that the number of waveforms of the error amplification signal EAO11 within the same counting time length, that is, the number of counts (corresponding to the charge and discharge speed of the capacitor C1) is The error amplified signal EAO1 is twice. In other words, the gain Gain depends on the adjusted value of the capacitor C1 and the adjusted current value provided by the variable current source IREF.

Since the capacitance value of the variable capacitor C1 is adjusted according to the photocurrent Iph value, each of the error amplification signals EAO1 and EAO11 output by the operational amplifier 100 has multiple waveforms except for the first waveform that is initially adjusted. It has the same amplitude and period, and the period of each waveform is less than the time threshold.

[Second Embodiment]

Please refer to FIG. 4, which is a circuit layout diagram of an ambient light sensor applied to an electronic device according to a second embodiment of the present invention. As shown in FIG. 4, the ambient light sensor 10 according to an embodiment of the present invention includes an operational amplifier 100, a comparator 200, a logic circuit 300, a pulse wave accumulator circuit 410, a pulse wave generation circuit 500, a pulse wave storage circuit 610, and a photoelectric Elements PD1, PD2, fixed capacitor C2, current mirror circuit M1, and switching elements S1, S2.

The difference between the second embodiment and the first embodiment is that the capacitor C1 of the first embodiment is a variable capacitor; and the capacitor C2 of the second embodiment is a fixed capacitor or an invariable capacitor (which can also be replaced by a variable capacitor in implementation) And, the ambient light sensor 10 is additionally provided with a pulse wave generating circuit 500. The pulse wave generating circuit 500 is connected to the control terminal of the switching element S1, the output terminal of the logic circuit 300, and the input terminal of the pulse wave accumulator circuit 410. In addition, the logic circuit 300 of the first embodiment is connected to an additional clock generation circuit to trigger the logic circuit 300 through the positive edge of the clock signal CLKL1, and the setting terminal SET of the logic circuit 300 of the second embodiment is connected to the output of the comparator 200 Outside the terminal, the reset terminal RESET is connected to the output terminal of the comparator 200 through an inverse OR gate.

In practice, the photocurrent Iph generated by the photoelectric element PD1 continues to discharge the fixed capacitor C2. The discharge time is inversely proportional to the light intensity of the ambient light source. The operational amplifier 100 multiplies the difference between the input voltage of the inverting input terminal of the operational amplifier 100 and the voltage of the reference voltage source VREF and the gain, and outputs the corresponding error amplification signal EAO2.

When the voltage value of the waveform of the EAO2 comparison error amplification signal of the comparator 200 is greater than the voltage value of the reference voltage source VREF, the comparator 200 outputs the comparison signal CMP2 representing logic 1 to the setting terminal SET of the logic circuit 300 and an input of an OR gate end. When the setting terminal SET of the logic circuit 300 receives the comparison signal CMP2 representing logic 1, the logic circuit 300 outputs the logic signal LOG2 representing logic 1 through the output terminal Q to the input terminal of the pulse wave accumulator circuit 410, the pulse wave accumulator The circuit 410 counts to generate the number of times CON2 to be stored in the pulse wave storage circuit 610, or to update the original number of times CON2 stored by the pulse wave storage circuit 610.

It is worth noting that when the logic circuit 300 outputs the logic signal LOG2 to the pulse wave accumulator circuit 410, it can output the logic signal LOG2 to the pulse wave generation circuit 500 to After the pulse wave accumulator circuit 410 finishes counting, the logic circuit 300 is reset. More specifically, when the comparison signal CMP2 received from the comparator 200 at one input terminal of the NOR gate and the pulse signal PG2 received from the pulse wave generation circuit 500 at the other input terminal of the NOR gate are both When logic 0, the OR gate generates a signal representing logic 1 to the reset terminal RESET of the logic circuit 300 to reset the logic circuit 300.

The comparison signal CMP2 has a rising or falling edge alignment error amplification signal EAO2 waveform whose voltage rises from a voltage less than the reference voltage source VREF to an instant that is not less than the voltage of the reference voltage source VREF. At the instant of the waveform of the error amplification signal EAO2, the pulse accumulator circuit 410 counts the input voltage of the non-inverting input terminal of the comparator 200 from a voltage less than the reference voltage source VREF to a voltage greater than the reference voltage source VREF based on the comparison signal CMP2 The number of voltages CON2.

In other words, when the voltage of the waveform of the error amplification signal EAO2 rises from a voltage less than the reference voltage source VREF to a voltage greater than the reference voltage source VREF, the pulse wave accumulator circuit 410 performs a counting operation, so that the pulse wave accumulator circuit 410 The count count CON2 is correct without omission. Accordingly, the control circuit 30 of the electronic device can accurately adjust the screen brightness of the electronic device according to the correct number of counts CON2 counted by the pulse wave accumulator circuit 410.

On the other hand, the pulse wave generating circuit 500 can control the operation of the switching element S1 according to the value of the logic signal LOG2 output by the logic circuit 300, the count times and the time. When the pulse wave generating circuit 500 outputs a low-level pulse signal to turn on the switching element S1, the current provided by the constant current source IREF2 flows through the switching element S1 to other circuit elements such as the capacitor C2 shown in FIG.

[Third Embodiment]

Please refer to FIG. 5, which is a circuit layout diagram of an ambient light sensor applied to an electronic device according to a third embodiment of the present invention. As shown in FIG. 5, the ambient light sensor 10 according to an embodiment of the present invention includes an operational amplifier 100, a comparator 200, a logic circuit 300, a pulse wave accumulator circuit 410, a pulse wave generation circuit 500, a pulse wave storage circuit 610, and a photoelectric Components PD1 PD2, variable capacitor C1, current mirror circuit M1, and switching elements S1, S2. In this embodiment, the fixed capacitor C2 of the second embodiment is replaced with a variable capacitor C1. Or alternatively, in yet another embodiment, a pulse wave generating circuit 500 is added to the circuit of the first embodiment, and the configuration method refers to the second embodiment. Therefore, this embodiment and still another embodiment can increase the configuration of the variable capacitor C1 and the pulse wave generating circuit 500 so that the electronic device 1 can adjust the display screen in real time to have a more satisfactory brightness.

Please refer to FIG. 6 together, which is the error amplification signal output by the operational amplifier of the ambient light sensor of the third embodiment of the present invention, the comparison signal output by the comparator, the logic signal output by the logic circuit, and the pulse accumulator circuit The number of counts and the waveform diagram of the enable signal input to the pulse wave storage circuit. As shown in FIG. 6, the reference voltage source VREF input to the operational amplifier 100 and the comparator 200, the error amplification signal EAO3 output from the operational amplifier 100, the comparison signal CMP3 output from the comparator 200, and the logic circuit are in order from top to bottom. The logic signal LOG3 output by 300, the number of times CON3 output by the pulse wave accumulator circuit 410, and the waveform of the enable signal IT_EN input to the pulse wave storage circuit 610.

When the voltage value of the error amplification signal EAO3 rises to exceed the voltage value of the reference voltage source VREF, the comparator 200 outputs the high-level comparison signal CMP3 to the setting terminal SET of the logic circuit 300. As shown in FIG. 6, the voltage value of each waveform of the error amplification signal EAO3 rises from a voltage less than the reference voltage source VREF to an instantaneous point equal to the reference voltage source VREF, and the alignment signal CMP3 waveform transitions from the low logic level 0 It is the rising edge between high logic level 1.

When the setting terminal SET of the logic circuit 300 receives the high-level comparison signal CMP3, the logic circuit 300 outputs the high-level logic signal LOG3 to the pulse wave accumulator circuit 410, triggering the pulse wave accumulator circuit 410 to count the non-comparison of the comparator 200 The number of times the voltage at the inverting input terminal rises from a voltage less than the reference voltage source VREF to a voltage greater than the reference voltage source VREF, CON3, that is, the number of waveforms of the count comparison signal CMP3.

That is to say, the rising edge of the waveform of the error amplification signal EAO3 gradually rises as the photocurrent Iph discharges the capacitor C1 until the voltage of the capacitor C1 rises above the voltage of the reference voltage source, the falling edge of the waveform of the error amplification signal EAO3 As the current provided by the variable current source IREF gradually decreases the charging operation of the capacitor C1, the logic signal LOG3 generates a pulse wave with each charge and discharge operation, and the pulse wave accumulator circuit 410 counts the pulse wave over a period of time The number, that is, the number of times the capacitor C1 performs charge and discharge operations.

Because the circuit elements of the ambient light sensor can transmit signals very quickly, the voltage value of each waveform of the error amplification signal EAO3 rises from a voltage less than the reference voltage source VREF to equal to the reference voltage source VREF, the pulse wave accumulator circuit 410 basically performs counting operations.

In addition, the logic circuit 300 can output a high-level logic signal LOG3 to the pulse wave generating circuit 500. The pulse wave generating circuit 500 then outputs the pulse signal PG3 corresponding to the logic signal LOG3 to the NOR gate of the reset terminal RESET connection of the logic circuit 300, for example, the pulse signal PG3 has the same pulse as the logic signal LOG3 shown in FIG. 6 The wave width makes the waveform of the error amplification signal EAO3 discharge the capacitor C1 within the time of this pulse width. After the time of the pulse width ends, the pulse wave generating circuit 500 switches from the high level to output the low level pulse signal PG3 to the NOR gate, and the comparison signal CMP3 as shown in FIG. 6 is also at the low level, triggering The logic circuit 300 performs a reset operation. After the reset, the logic circuit 300 turns to output the low-level logic signal LOG3.

As mentioned above, the error amplification signal EAO3 has discharged C1 to a low level within the pulse width time. When the photocurrent Iph flowing out of the capacitor C1 gradually increases, the voltage of the capacitor C1 climbs upward again. When the voltage of the next waveform of the error amplification signal EAO3 shown in FIG. 6 rises above VREF, the above operation is repeated again. .

Please refer to FIG. 7 and FIG. 8 together. FIG. 7 is a graph of the photocurrent generated by the photoelectric element of the ambient light sensor according to the third embodiment of the present invention versus the number of counts of the pulse accumulator circuit. FIG. 8 is a conventional environment Photocurrent pair counting circuit of photoelectric element of photo sensor The graph of the number of counts. As shown in FIGS. 7 and 8, the horizontal axis is the current value of the photocurrent, and the vertical axis is the number of counts by the counting circuit and the pulse wave accumulator circuit.

Obviously, the curve of the conventional ambient light sensor shown in FIG. 8 is irregular. This means that the clock generation circuit of the conventional ambient light sensor generates a fixed clock signal waveform, resulting in the voltage value of each waveform at the output of the error amplification signal rising from less than the reference voltage source to equal to the reference voltage source. At the instant, the error amplification signal EAO3 as shown in FIG. 6 may not be aligned with the rising edge of the pulse signal, so the counting circuit is not triggered to count, so that the number of counts by the counting circuit is missing, which may cause the brightness of the display screen of the electronic device Inaccurate and non-linear adjustment.

In contrast, the curve of the ambient light sensor in the embodiment of the present invention shown in FIG. 7 is linear, which means that the voltage at the non-inverting input of the comparator 200 can rise from less than the reference voltage source to greater than At the instant of the reference voltage source VFEF, the pulse wave generating circuit 500 generates the corresponding pulse signal PG3, triggering the pulse wave accumulator circuit 410 to count the voltage of the non-inverting input terminal of the comparator 200 to rise from less than the voltage of the reference voltage source VREF to greater than The number CON3 of the voltage of the reference voltage source VREF. Therefore, the embodiments of the present invention can effectively improve the accuracy of adjusting the screen brightness of the display screen of the electronic device.

[Beneficial effect of embodiment]

The beneficial effect of the present invention is that the ambient light sensor provided by the present invention can increase the configuration of the variable capacitance and the pulse wave generating circuit and other circuit elements, so that only a small number (only two) of photoelectric elements can be provided to save the circuit Under the conditions of component configuration cost and reduced space occupation, the light intensity of the ambient light source can be accurately sensed in a short time, so that the electronic device can adjust the display screen to have a more desirable result according to the sensing result of the ambient light sensor brightness.

Finally, it should be noted that, in the foregoing description, although the technical concept of the present invention has been specifically illustrated and described in a number of exemplary embodiments, those with ordinary knowledge in the field of this technology will understand that Deviation is bounded by the scope of the following patent applications Given the scope of the technical concept of the present invention, various changes in form and details can be made.

10‧‧‧Ambient light sensor

100‧‧‧Operational amplifier

EAO3‧‧‧Error amplification signal

200‧‧‧Comparator

CMP3‧‧‧comparison signal

300‧‧‧Logic circuit

SET‧‧‧Setting

RESET‧‧‧Reset

‧‧‧輸出端 Q,

‧‧‧Output

LOG3‧‧‧Logic signal

410‧‧‧Pulse Accumulator Circuit

CON3‧‧‧ times

610‧‧‧pulse wave storage circuit

REG3‧‧‧save signal

500‧‧‧Pulse wave generating circuit

PG3‧‧‧Pulse signal

PD1, PD2

Iph‧‧‧Photocurrent

Idark‧‧‧Dark current

C1‧‧‧Variable capacitance

M1‧‧‧ Current mirror circuit

T1, T2‧‧‧transistor

S1, S2‧‧‧Switch element

SH‧‧‧Shading element

VREF‧‧‧Reference voltage source

IREF‧‧‧Variable current source

20‧‧‧Capacitance control circuit

30‧‧‧Control circuit

IT_EN‧‧‧Enable signal

Claims (10)

An ambient light sensor is suitable for an electronic device. The electronic device includes a capacitance control circuit. The ambient light sensor includes: a first photoelectric element having a first positive terminal and a first negative terminal. The first positive terminal of the first photoelectric element is grounded, the first photoelectric element is configured to convert the light energy irradiated through the first photoelectric element into a photocurrent; a variable capacitor is connected to the capacitance control circuit, and the capacitance control The circuit is configured to adjust a capacitance value of the variable capacitor according to the photocurrent value, the variable capacitor receives the photocurrent; an operational amplifier has a first amplification input terminal and a second amplification input terminal, respectively connected to the first The first negative terminal and a reference voltage source of a photoelectric element, the variable capacitor is connected between the output terminal of the operational amplifier and the first amplification input terminal, and the operational amplifier is configured to be based on the voltage of the first amplification input terminal and The voltage difference of the reference voltage source and the gain value of the operational amplifier output an error amplification signal; a comparator has a first comparison input terminal and a second comparison input terminal, respectively connected to the output of the operational amplifier Terminal and the reference voltage source, the comparator is configured to compare the error amplification signal with the reference voltage source to output a comparison signal; a pulse wave generating circuit is connected to the output terminal of the comparator, and is configured according to the ratio When it is judged that the voltage of the first comparison input terminal of the comparator is greater than the voltage of the reference voltage source, a pulse signal with a rising or falling edge of the waveform aligned with the voltage waveform of the first comparison input terminal is output When the voltage of the reference voltage source rises to an instant no less than the voltage of the reference voltage source; and a pulse wave accumulator circuit connected to the pulse wave generating circuit and the output terminal of the comparator, the pulse wave accumulator circuit is configured Based on the comparison signal, the voltage at the first comparison input terminal rises from less than the voltage of the reference voltage source to greater than the parameter When the voltage of the voltage source is tested, the counting is realized. The ambient light sensor according to claim 1, further comprising a second photoelectric element and a light blocking element, the light blocking element is configured to shield the second photoelectric element to prevent light from passing through the second photoelectric element, the second The photoelectric element is connected in parallel to the first photoelectric element, the second photoelectric element has a second positive terminal and a second negative terminal, respectively grounded and connected to the first amplification input terminal of the operational amplifier, and the second photoelectric element outputs a Dark current. The ambient light sensor according to claim 2, wherein the electronic device further includes a control circuit configured to obtain the photocurrent value of the first optoelectronic element and the dark current value of the second optoelectronic element, and The photocurrent value is subtracted from the dark current value to obtain an ambient photocurrent value, and the light intensity is determined according to the ambient photocurrent value. The ambient light sensor according to claim 2 further includes a current mirror circuit, an input terminal of the current mirror circuit is connected to a voltage source or a current source, and two output terminals of the current mirror circuit are respectively connected to the first photoelectric element The first negative terminal and the second negative terminal of the second photovoltaic element. The ambient light sensor according to claim 1, further comprising a logic circuit connected between the comparator and the pulse wave accumulator circuit, the logic circuit is configured to receive the comparison signal output by the comparator, And convert the comparison signal into a logic signal and output it to the pulse wave accumulator circuit. The ambient light sensor according to claim 5, wherein the logic circuit is an S-R type flip-flop. The ambient light sensor according to claim 1, further comprising a pulse wave storage circuit connected to the pulse wave accumulator circuit, configured to store the pulse wave accumulator circuit to count the voltage of the first comparison input terminal of the comparator The number of times the voltage of the waveform rises from a voltage less than the reference voltage source to no less than the voltage of the reference voltage source. The ambient light sensor according to claim 1, further comprising a current source connected to one end of the variable capacitor connected to the first amplification input end of the operational amplifier, the current source providing current flow Through the variable capacitance, the current source contains A variable current source, a certain current source, or a combination thereof, the capacitance control circuit is configured to adjust the current value of the variable current source according to the photocurrent value. The ambient light sensor according to claim 8, further comprising a first switching element, a first end, a second end and a control end of the first switching element are respectively connected to the current source and the operational amplifier The first amplifying input terminal and the pulse wave generating circuit. The ambient light sensor according to claim 1, further comprising a second switching element connected between the output terminal of the operational amplifier and the first amplification input terminal of the operational amplifier, the first Two switching elements are connected in parallel with the variable capacitor.

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